Update git submodules

* Update docs/submodules/openretriever from branch 'master'
  - workaroud k8s deploy issue

    use kubeadm 1.7.0 to workaround deploy issue:
    https://github.com/kubernetes/kubernetes/issues/49065

    Change-Id: I94802e3164c175515fd9934c8cd55ca8f90a8bd9
    Signed-off-by: Guo Ruijing <ruijing.guo@intel.com>

diff --git a/docs/submodules/openretriever b/docs/submodules/openretriever
index b4804ed..5e53d80 160000 (submodule)
--- a/docs/submodules/openretriever
+++ b/docs/submodules/openretriever
@@ -1 +1 @@
-Subproject commit b4804ed0b8d88fc91324dfbbf9e285d0691bb0f4
+Subproject commit 5e53d80ca4d3fbcf095b4e02d36b4e28fd7af00f